Dean’s Blue Hole is said to be the deepest blue hole in the world, and the second largest underwater chamber. Experts at Reeldivers and Vertical Blue, who have done dives at the site, report that: “It is enclosed on three sides by a natural rock amphitheatre, and on the fourth side by a turquoise lagoon and powder white beach. There is never any swell or waves inside the Hole, and visibility is usually between 50 – 100 feet (15 – 30m).”
The Blue Hole dips some 663 feet (203 meters) into the ocean floor right off shore. At the surface it is 80 x 120 feet (25 x 35m), but opens out after 60 feet (20m) into a cavern with a diameter of at least 330 feet (100m).
It is located west of Clarence Town on Long Island, Bahamas., and is also the site where the Freediving World Record was set in April 2007.
Blue hole is a term for water-filled sinkholes with the entrance below the water level. They can be formed in different karst processes, for example, by the rainwater soaking through fractures of limestone bedrock onto the watertable. Sea level here has changed: for example, during the glacial age during the Pleistocene epoch (ice age), some 15,000 years ago, sea level was considerably lower. The maximum depth of most other known blue holes and sinkholes is 110 metres (360 ft), which makes the 203 metres (666 ft) depth of Dean’s Blue Hole quite exceptional.
Dean’s Blue Hole is roughly circular at the surface, with a diameter ranging from 25 to 35 metres (82–115 ft). After descending 20 metres (66 ft), the hole widens considerably into a cavern with a diameter of 100 metres (330 ft).
There are several freshwater water-filled sinkholes on land that are deeper than Dean’s Blue Hole. These include the 270 m (890 ft) Boesmansgat in South Africa, Mexico’s Zacatón at 335 metres (1,099 ft) and the 392 metres (1,286 ft) Pozzo del Merro in Italy.
There is a great variety of sea animals to be found inside Dean’s blue hole. Snorkelers and divers alike will be able to spot snapper fish, tarpons, turtles seahorses, rays and many colourful tropical fish.